Contact-resistance lamp



c F LORENZ CONTACT RESISTANCE LAMP Filed Aug. 1, 1924 March 11, 1930.

Patented Mar. 11, 1930 UNITED STATES PATENT? OFFICE CHARLES FREDERICKLORENZ, 0F EAST ORANGE, NEW JERSEY, ASSIGNOR TO WEST- INGHOUSE LAMPCOMPANY, A CORPORATION OF PENNSYLVANIA CON TACT-RESISTAN CE LAMPApplication led August 1, 1924. Serial No. 729,463.

This invention relates to an incandescent electric lamp and moreparticularly to a contact resistance lamp in which the light is producedby two or more electrodes in contact.

Lamps of this nature are operated at relatively low voltage and at highamperage, and the electrodes are locally heated to incandescence attheir contacting surfaces due to the imperfect contact between theelectrodes or because 0f the limited area of such contact.

This lamp is, in some respects, similar to an arc lamp in that one ormore of the electrodes may be slowly consumed and in such case, meansmust be provided for feeding the electrodes together to maintain aconstant and uniform contact therebetween. No appreciable arc, however,is formed.

The electrode material, vaporized from'the electrodes in lamps of thistype, as heretofore constructed, rendered the operation of the lampunsatisfactory because of the deposition of the vaporized material onthe wallof the envelope with consequent blackening and discolorationthereof and'loss of eificiency.

One of the objects of this invention is to produce a contact resistancelamp in which discoloration of the bulb is prevented or localized so asnot to impair the eiiciency of the lamp.

Another object is t0 produce a contact resistance lamp which will have ahigh eiliciency and high candle power maintenance.

Another object is to produce an incandescent lamp having a concentratedlight source continuous over its entire extent.

Another object is to provide a contact resistance lamp in which thecontacting surfaces of the electrode are enclosed.

Another object is to shield that portion of the bulb through which it isdesired to transmit the light from the blackening effect of thevaporized electrode material.

Other objects and advantages will hereinafter appear.

In accordance with this invention, a plurality of electrodes arearranged with a portion of their surfaces in contact within an exhaustedor s-iilled envelope. The electrodes shoulireferably be composed ofmaterial of such nature that they will not stick or become fusedtogether during the operat1on of a lamp. Carbon, in one of its variousforms, is particularly suitable for this purpose, particularly thegraphitic form of carbon. One or more of the electrodes, however,

may be composed of refractory metal, such as tungsten or molybdenum oralloys thereof.

The area of contact between the electrodes should be relatively small orthe contact sufliciently imperfect to produce a high resistance to theflow of the high amperage current at the point of contact, whereby thelocal heatlng of the electrodes at their points of contact, will besufficient to render them incandescent and thus produce an illuminatingsource.

In order to suppress vaporization of the electrodes, the envelope may befilled with an inert gas such as argon or a mixture of inert gases,preferably at a pressure of about one atmosphere. i

In o rder to prevent the vaporized electrode materlal from depositing onthe bulb or on that portion thereof through which it is deslred totransmit the light, a shield may be arranged around the electrodes.

-Thls shield may be apertured to permit the light to be transmittedtherethrough or it may be formed in part by one of the electrodes, theother electrode contacting with the inner surface thereof whereby thevaporlzatlon of the electrode material occasioned b y local heating,takes place practically entirely on the inside of the shield.

Means may also be provided for feeding one or both of the electrodes astheyI are consumed to` maintain them continuously in contact at asubstantially uniform pressure.

In order that this invention may be more fully understood, referencewill be had to the accompanying drawings in which' Fig. 1 isa sectionalview of/one form of contact resistance lamp embodying this invention;and,

Fig. 2 is a sectional view of a modified form of such a lamp.

The contact resistance lamp shown in Fig. 1 comprises in general, a bulb1 containing an inert as, as argon, or a mixture of inert gases an apair of electrodes 2 and 8 electrically connected to and suitablysupported from terminals 4 and 5. Y

The electrode 2 is in thel form of a thin l disc or wafer of carbon orother refractory material having a high specific resistance and 1ssupported 1n the recessed end ot' a (-yhudrical shield 7 which may beformed of any suitable conducting material such as carbon or metalthreaded or otherwise suitably secured to the outer end otl a metal tube8, the opposite en'd of which is threaded internally of the terminal 4of the lamp. The terminal 4 is composed of a metal, as copper, and isjoined to the neck 9 of the bulb and to au insulating ring 10 or sleeveof glass or other suitable material in a manner well known in the art.The terminal 5 is similarly secured to the opposite end of theinsulating sleeve The electrode 3 is in the form of a pencil of carbon,metal or other conducting 1naterial, having an enlarged rear end 11 bywhich it is secured to a metal tube 12 by threads 13. The tube 12 isarranged concentric with respect to the tube 8 and spaced therefrom by aring 14 of insulating ma terial, such as mica. The lower end of the tube12 slidin ly engages a rod 15 of metal or other con uptin materialrigidly supported by the terminal 5 of the lamp. A coiled spring 16 maybe interposed between the end of the tube 12 and the inner surface ofthe terminal 5 to exert a constant pressure upon the tube 12 so as tomaintain the electrode 3 in constant contact with the electrode 2 and tofeed the electrode 3 upwardly as it is consumed. In order to make a goodcontact between the rod 15 and the tube 12, the lower end ofthe lamp maycontain a quantity of mercury 17.

It will thus be noted that the point of contact 18 between theelectrodes 2 and 3, is totally enclosed and any vaporization that takesplace at the electrode surface will be 'deposited on the inner surfaceof the cylinder 7 or on the tubes 8 and 12. In order,

however2 to revent an excessive pressure from belng eveloped within theshield or casing which surrounds the electrodes, the tube 8 may have aperforation 19 therein through which the pressure will be equalized onboth sides of the shield. y

The high resistance interposed in the circuit by the limited contactarea between the electrodes 2 and 3 will produce local heating at thepoint of contact and since the disc electrode 2 is relatively thin, thisheat will be transmitted through the disc and render the outer surfacethereof incandescent. Moreover, the current density in the wafer or disc2 will be high, due to the relatively small sectional area thereof whichwill also aid in heating this electrode. The cylindrical casing orshield 7, however, because of its relatively large area, will not behighly heated.

The incandescent button or wafer 2 constitutes a concentrated brilliantlight sourceot substantially uniform intensity throughout it s entireexposed area. This type of a light source is particularly adapted forthe operation of projection apparatus.

In Fig. 2, a modified form of contact resistance lamp is shown in whichthe light is produced by means of a stack or plurality of wafers or thindiscs 20. These discs may be dish-shaped or recessed as at 21 wherebythey may be nested one within the other, to assist in maintaining themin proper relation. A pair of metal conductors 22 and 23 are providedfor the outer electrodes 24 and 25 of the series of contactingelectrodes. The conductor 22 is supported from and is in electricalcontact with an external terminal 26. The conductor 23 is threaded orotherwise suitably secured in a carbon or metal block 27 which slidinglyengages a metal conductor 28 suitably supported by and in electricalcontact with the terminal 29. A helical spring 30 may be'interposedbetween the low'- er end of the block 27 and the inner surface oftheterminal 29 to maintain the discs 20 in continuous contact atsubstantially uniform pressure.

The terminals 28 and 29 are suitably joined to the envelope 31 in a gastight manner and the envelope is provided with a filling of rare gas tosuppress vaporization of the electrodes.

A shield or sleeve 32 of suitable refractory material such as molybdenumis arranged around the discs 20 and is apertured at 33 to permit thelight from the disc to be transmitted therethrough. The shield may besupported by a spider 34 from the conductor 22, although, of course, anyother suitable supporting means may be provided. The shield or sleeve 32serves somewhat as a chimney in directing the vaporized material awayfrom the aperture 33 and out of the upper end thereof so that theelectrode materlal is deposited on the inner wall of the shield or inthe upper end of the lamp where it will not obstruct the lighttransmitted through the aperture 33.

It will be noted that a lamp has been produced which has a concentratedlight source of practically uniform intensity over its entire exposedarea and that blackening of the' said means having an aperture forpermitting the light emitted from the opposite side of said incandescentbody to be transmitted through the Wall of the envelope.

2. A contact resistance lamp comprising an envelope containingelectrodes in contact, means for feeding said electrodes together asthey are consumed, and means for enclosing the contacting portions ofsaid electrodes to prevent the deposition of electrode material onpredetermined portions of the envelope.

3. An incandescent electric lamp comprising an envelope, a comparativelythin electrode therein, asecond electrode contacting with one side ofsaid lrst electrode to heat the same to incandescence, a shieldinterposed between said contacting surfaces and the Walls of thecontainer said shield having means for exposing a portion of said rstelectrode to produce a concentrated continuous light source.

4. A contact resistance lamp comprising an envelope, an electrode in thesaid envelope, means for preventing the deposition of vaporizedelectrode material upon the Wall of said envelope, another electrode insaid envelope and in contact with said first mentioned electrode andmounted to cooperate With said means for preventing the deposition ofvaporized material.

5. A contact resistance -electric incandescent lamp comprising anenvelope, a plurality of electrodes therein, a refractory shieldsurrounding said electrodes to prevent the deposition of electrodematerial on the wall of said envelope, one of said electrodescooperating with said shield to prevent said deposition.

6; An incandescent electric lamp comprising a container, a pair ofcontacting electrodes within said container, an enclosure for partiallysurrounding said electrodesto prevent the deposition of vaporizedmaterial upon the walls of said container, one of said electrodescooperating with said enclosure to prevent said deposition, and meansfor equalizing the pressure on opposite sides of said enclosure.

7. A contact resistance lamp comprising a container, a plurality ofelectrodes therein havinosurfaces in contact, means for partiallyenclosing the contact portions of said electrodes, one of saidelectrodes coo rating with said means to completely enc ose the saidcontacting portions, and means for cqualizing the pressure at oppositesides of said enclosing means.

In testimony whereof, I have hereunto Sllbu scribed my name this 30thday of July, 1924. CHARLES FREDERICK LORENZ.

